Metal oxide semiconductor field effect transistors (MOSFETs) are transistors commonly used for switching electric signals. MOSFETs may be p-type or n-type. A p-type MOSFET (pMOS) typically includes a p-type substrate, an n-well region located within the p-type substrate, a p-type source located within the n-well region, a p-type drain located within the n-well region, a n-well substrate terminal located within the n-well region and an oxide-insulated gate located on top of the n-well region. A voltage on the oxide-insulated gate induces a conducting channel in the n-well region between the source and drain.
In fabricating a p-type MOSFET (pMOS), several processes including plasma-based processes may be performed. Because plasmas comprise charged particles, exposure of the pMOS to plasma induces charged particles within the source, drain, and n-well substrate terminal of the pMOS. These charged particles flow from the drain, source, and n-well substrate terminal into the n-well region of the pMOS. Charged particles built up within the n-well region may then be discharged through the n-well region/p-type substrate junction. However, if the magnitude of charged particles accumulated in the n-well region becomes too great, charged particles residing in the n-well region will also discharge through the gate oxide of the pMOS. This may cause damage to the gate oxide of the pMOS as well as significant degradation in the performance of the pMOS.
Prior approaches involve adding an n-well protection diode within the p-type substrate of the pMOS to help provide additional discharge to the n-well region. However, n-well protection diodes only provide a limited path for additional discharge, which may fail to sufficiently protect the gate oxide from charge damage. Additionally, the n-well protection diode is essentially ineffective for protecting against front-end of the line (FEOL) plasma-based processes.